Attitudes of dump trucks operating at mines and construction sites are expressed by roll, pitch, and yaw angles. If a plane crossing perpendicularly to a gravity direction is defined as a horizontal plane, the pitch angle is an angle that an anteroposterior axis of a dump truck defines with the horizontal plane when rotating around a lateral axis (a side axis) crossing perpendicularly to the anteroposterior axis, and the roll angle is an angle that the lateral axis defines with the horizontal plane when rotating around the anteroposterior axis. An azimuth is the yaw angle that is a rotational angle of the vertical axis crossing perpendicularly to both the anteroposterior axis and the lateral axis.
A well-known technology as described in JP-2012-233353-A, relating to dump trucks, uses two position estimation devices, such as global positioning systems (GPS), to measure the azimuth (yaw angle) of construction machinery, and uses an inertial measurement unit with a combination of a gyro-sensor and an acceleration sensor to estimate roll and pitch angles of the construction machinery. Such a technology thus estimates an attitude of a hydraulic shovel, a type of construction machinery.
JP-2010-190806-A discloses other means for estimating attitudes: a method of estimating attitudes by three position estimation devices on a general moving body.